Timing circuit

ABSTRACT

An electronic timing circuit that utilizes a three-element glow discharge lamp and operates from either alternating current or direct current power sources to provide a direct current control voltage upon completion of a desired timing interval, for example, when the power source is interrupted for more than a predetermined period of time and is then restored. A predetermined time delay is provided before the direct current control voltage is removed following removal of the power source. Another time delay is provided before the direct current control voltage returns following restoration of the power source. The circuit includes independently operable reset means which can be operated either locally and manually or by a remotely operated electronic circuit arrangement.

United States Patent 11 1 Adams 5 v June4,1974

[54] TlMlNG cmcunr [76] Inventor: William M. Adams, 746 Oak Ln.,

Bryan, Tex. 77801 [22] Filed: Dec. 8, 1972 211 Appl. No.: 313,405

[52] U.S. C1. 307/141, 317/142 R [51] 1111. C1. H0lh 7/00, H0111 43/00 [58] Field of Search ..317/151, 142 R, 141;"

328/210; 307/106 315/234, 168 56 References Cited ,UNlTED STATES PATENTS 2,747,145 5/195 Chubb et 211. 317 142 R 2,797,368 6/1957 Holden 315/168 Aitel 317/142 R Primary Examiner-David Smith, Jr. 1 Attorney, Agent, or FirmBerman, Bishoff Platt [57] ABSTRACT An electronic timing circuit that utilizes a threeelement glow discharge lamp and operates from either 1 alternating current or direct current power sources to provide a direct current control voltage upon completion of a desired timing interval, for example, when the power source is interrupted for more than a predetermined period of time and is then restored. A predetermined time delay is provided before the direct current control voltage is removed following removal of the power source. Another time delay is provided before the direct current control voltage returns following restoration of the power source. The circuit inv cludes independently operable reset means which can be operated either locally and manually or by a remotely operated electronic circuit arrangement.

10 Claims, 1 Drawing Figure Sup/ 1. Y

TO BE Call/TROLL ED TIMING CIRCUIT This invention relates to electronic timing circuits and more particularly to a timing circuit for use between a supply source and a device to be controlled for providing a time delay between the application of the power source and the actuation of said device and simiof electrical power and a device to be operated thereby, the circuit having high stability, being immune to noise, providing accurate timing, being operable satisfactorily with wide input voltage variations, providing visual indications of completed timing intervals, being adaptable for remote programming of the timing intervals or for remote reset control and operating automatically to safely restore power to a device to be controlled after a power supply interruption.

A-further object of the invention is to provide an improvedelectronic timing circuit utilizing a threeelement glow discharge lamp both as a working circuit element and as an indicating means to provide visual indications of completed timing intervals, the improved circuit having highly accurate timing characteristics I and providing dependable operation over long periods of time.

A still further object of the invention is to provide an improved timing circuit which provides automatic resetting of the time interval whenever the line source is removed for more than a predetermined period of time and is thensubsequently restored.

A still further object of the invention is to provide an improved timing circuit which provides resetting of its time interval by transistor switch action but is also adapted to provide resetting by mechanical switch action. 1

A still further object of the invention is to provide an improved timing circuit which generates a square wave DC output voltage after completion of a timing interval, the control voltage being quickly terminable by reset means provided in the circuit.

A still further object of the invention is to provide an improved electronic timing circuit having multiple input resetting controls of its timing interval.

A still further object of the invention is to provide an improved electronic timing circuit adapted to provide remote programming of its timing interval.

A still further objectof the invention is to provide an improved electronic timing circuit which is not susceptible to line voltage source conditions of various types such as line voltage flicker" but which is rapidly responsive to other line voltage conditions, such as substantial voltage deterioration or power stoppage.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawing wherein the single'figure represents a typical circuit diagram embodying the present invention.

Prior art devices such as that disclosed in US. Pat. No. 3,657,603 to William M. Adams disclose the need for a timing circuit which is stable with respect to wide source voltage variations and which can be reset by either transistor or mechanical switches. The present invention aims to accomplish the desired purposes by employing the stable characteristics of gas filled glow lamps. The stability of the two-element gas filled glow lamp is well known. The addition of a third element provides additional control for ionization of such a glow lamp. Glow lamps normally operate at very low current values and require certain biasing voltage limitations. In a three-element glow lamp, one of such limitations is that the voltage level between two elements, commonly known-as the anode" and gate" must not exceed a certain level to avoid unwanted ionization. The circuit of the present invention includes means to efficiently regulate such voltage levels.

- which may be either alternating current or direct cur- Referring to the drawing, 11 generally designates a device to be operated or controlled from a pair of supply terminals 1 and 2, which may be connected to a suitable source of alternating current or direct current. The device 11 may be any suitable known apparatus for controlling equipment to be energized from the power supply terminals through suitable circuits, not shown, the device 11 being connected in a well known manner so as to open and close the circuits. Thus, as a typical example, the device ll may comprise a control relay or relay circuit connected so as to control the energization and deenergization of a load device or load circuit adapted to be energized from the power supply.

The device to be controlled, namely, the device 11, is activated by the present of a control voltage V across the input terminals of said device 11. Thus, the device 11 drops out when the control voltage V is removed.

As shown in the figure, the power supply voltage,

rent, is applied at the terminals 1 and 2, the terminal 2 being grounded. A diode D, is connected between the terminal 1 and a terminal 8, and a filter capacitor C is connected between terminal 8 and the grounded power terminal 2. Thus, when alternating current is applied at the terminals 1 and 2, the supply current will be rectified by the diode D, and filtered by the capacitor C providing a positive DC voltage at the point 8. If a direct current power supply is employed, when the positive supply wire is connected to the terminal 1 and the negative supply wire is connected to the terminal 2, diode D, will pass the current, again, providing a positive voltage at the terminal 8. If the negative supply wire is connected to the terminal 1, the diode D will not conduct, and therefore this diode serves as a reverse polarity protective device.

Connected in series between the terminal 8 and the ground are resistors R, and R forming a voltage divider network. Thus, when the above-mentioned positive DC voltage appears at the terminal 8, a voltage V appears at the junction 12 of resistors R, and R Junction 12 is connected through a capacitor C to the base of a transistor 0,, and a resistor R is connected between said base and ground. Thus, the capacitor C the resistor R and parallel input resistance of Q form a RC coupling network whereby the voltage V is applied to the base of the transistor Q, when the aforesaid positive DC voltage initially appears at the terminal 8, causing the transistor 0, to become momentarily forward biased and therefore momentarily to be conductive from its collector terminal 9 through its emitter to ground.

A capacitor C is connected from ground through a current limiting resistor R to the collector terminal 9 so that the resistor R, limits the collector current of charge through transistor 0,, namely, when said transistor is conductive.

It will be further seen from the drawing that the transistor terminal 9 is connected to a terminal 3. Grounding of this terminal will also cause the capacitor C to discharge through the current-limiting resistor R Terminal 3 may be connected to a conductor 13 which in turn may be at times connected to ground by use of a manually operated switch S, or alternatively, may be grounded by the conduction of transistors or 04 connected in parallel between conductor 13 and ground. Transistors O and Q represent typical electronic switch devices which maybe remotely controlled or' which may be programmed to become conductive at selected times in accordance with the re quirements for control of the device 11.

A transistor 0 is connected across the resistor R and the base of transistor 0 is connected through a resistor R to the control voltage terminal 4. Designated at L, is a gas filled three-element glow discharge lamp having the anode A, the cathode C and the gate electrode G. The three-element glow discharge tube may be of any suitable commercial type, for example, may be similar to type l20 TG27-2, manufactured by Signalite, Inc., a Division of General Instrument Corp., Neptune, NJ. A characteristic of this type of glow discharge lamp is that when sufficient voltage is applied between any two terminals, ionization of the gas therein will occur, resulting in increased current flow throughthe lamps ionized gas and associated biasing circuits. As shown in the drawing, the anode terminal A is connected at 14 to the junction between capacitor C and resistor R The cathode C is connected to the control voltage terminal 4 and the gate electrode G is connected to a terminal 15. A capacitor C is connected between terminal 15 and ground.

As will be presently explained, normally, the voltage applied to the anode terminal A is set to a level less than the ionization potential for the anode to cathode circuit, but more than the maintaining potential for this circuit. The gate electrode G may then be utilized to control ionization of the gas in the lamp L,. This control may be in the form of a slowly increasing voltage, which when of a suitable level, causes the gate-tocathode circuit to ionize, which in turn, causes the anode-to-cathode circuit current to increase quickly at the time of ionization. Ionization of the lamp L, will be maintained until such time that the voltage on the anode A is lowered below its maintaining voltage value.

The cathode C is connected through a ground return terminating resistor R to ground. The anode element A is connected to a'zener-regulating voltage terminal 16 through a resistor R Capacitor C connected to terminal 14, forms a RC circuit that charges when the circuit is first energized or the grounding functions at terminals 3 and 9 are removed. This reduces the voltage appearing on terminal'A of the lamp L, to below the ionization potential for the anode-to-gate and be less than the ionization potential for the anode-togate circuit. The gate electrode G is connected to the junction 15 of a RC circuit comprising a resistor R,,, and the capacitor C The resistor R is connected between the gate electrode terminal 15 and a zenerregulated voltage junction terminal 17. The zenerregulated voltage at the junction 16 is regulated by a zener diode D whereas the voltage at the junction 17 is regulated by another zener diode D,. As shown, the respective zener diodes D and D are connected between the terminals 16 and ground, and 17 and ground. respectively. Terminal 17 is connected to the positive voltage terminal 8 through a resistor R,,. A resistor R, is connected between the zener-regulated voltage terminals l6 and 17. A diode D is connected between the terminals 14 and 15. Another diode D is connected between the positive voltage terminal 8 and the junction terminal 15. A bleeder resistor R,, is connected between the positive voltage terminal 8 and ground.

The zener regulation by the diodes D and D or other equivalent voltage regulating devices which may be substituted therefor, stabilizes the bias voltages for the lamp L, which would otherwise vary due to source voltage variations at terminals 1 and 2.

It will be noted that when the capacitor C discharges to a voltage somewhat below the voltage level (charge) of capacitor C for example, a few tenths of a volt below this voltage level, the diode D becomes conductive and also causes capacitor C to discharge rapidly through the resistor R, and a low resistance circuit which may comprise either transistor Q, (when conductive) or a grounding circuit from terminal 3, namely, whichever circuit is conductive to ground from the collector terminal 9. A sustained ground at terminal 3.will prevent capacitors C and C, from charging.

When the circuit is energized by power applied at the terminals 1 and 2, the resetting action by the conduction of transistor Q, previously described occurs. Provided that reset terminal 3 is not at or near ground level, capacitor C, will commence charging to a value determined by the voltage rating of zener diode D and at a rate determined primarily by the parameters of the RC circuit comprising resistor R,, and capacitor C The voltage appearing on the anode terminal A of lamp L, with respect to time is therefore temporarily held below the ionization voltage level of the anode-to-gate circuit. Capacitor C continues to charge at a predetermined rate determined primarily by the effective series resistance of resistor R,,, toward a level equal to the regulated voltage provided by the zener diode D,.

A parallel resistor R,, may be connected in parallel with the resistor R, at terminals 6 and 7, for example, to lower the effective circuit value of the resistance in the charging circuit for purposes of remote programming or timing control.

When the voltage on the charging capacitor C, reaches a value corresponding to the ionization level for the gate'to-cathode' circuit of the lamp L,, the lamp will completely ionize and conduct and will provide a visual indication of this condition. The increased ionization current passing through the resistor R, will result in an increased direct current voltage drop across this resistor which will provide a continuous DC square wave control voltage V, at the terminal 4 until lamp L, is deionized. Transistor Q will then become forwardly biased and will conduct, reducing the voltage drop across resistor R to approximately 0. Capacitor C, will then discharge to a new lower voltage level. Under these conditions, the circuit can be considered as timed-out, and the normal output control voltage V would be present at terminal 4 for control or actuation of the device ill or other electronic devices or'electrical circuits to be controlled.

Resistor R limits the sustained ionization current of lamp L, and therefore allows the current through lamp L, and the cathode circuit of lamp L, to be controlled. Also, since the intensity of the visible light of lamp L, is a function of this ionization current, the brilliance and life expectancy of lamp L, may be controlled by selection of a desired value of resistor R,,.

As above-mentioned, the terminals 6 and 7 are provided to permit various values of resistance R to be connected in parallel with the resistor R Connection of such a resistor across the terminals 6 and 7 lowers the total resistance of the RC circuit including the resistor R,,, and the capacitor C.,, which will cause capacitor C to charge more rapidly and will cause lamp L, to ionize more quickly, since it more quickly brings the gate electrode to ionizing potential. Resistor R, may be of any suitable type, and may comprise a variable resistance, a resistance-selecting arrangement including a switch and respective resistors which may be connected thereby to the terminal 6 and 7 or may comprise conventional semi-conductor devices or circuits that exhibit resistor characteristics.

v Resistor R,, is connected as a conventional bleeder resistor, to cause capacitor C, to discharge at a rate in accordance with the time constant of the RC circuit defined by capacitor C, and resistor R,,, whenever the source of voltage is removed from the terminals 1 and 2. Thus, the discharge rate of capacitor'C, can be controlled by selecting a suitable value for resistor R,,. The energy stored in the capacitor C, will cause the lamp L, to remain ionized for a predetermined period of time following removal of the source voltage from the terminals l and 2. This effects a delayed deionization of lamp L, and therefore extends the period of time that the control voltage V is present at the terminal 4. This delay time is controlled by the selection of the appropriate values of the resistor R,, and capacitor C,. After the removal of the source voltage from the terminals 1 and 2, the lamp L, becomes deionized when the voltage applied to the anode terminal A of lamp L, falls below the necessary maintaining voltage level. Visual indication ofthe of condition will occur at this time by the deionization of the lamp L,.

Whenever the voltage at the point 8 falls a few tenths of a volt below the voltage across capacitor C diode D becomes forward biased (conductive). This causes capacitor C to discharge through the relatively lower resistance path provided by diode D and the resistor R,,, as well as certain of the other components. Thus, a delay period is required for capacitor C, tov charge whenever a permissible charge condition for capacitor C, is subsequently allowed.

Diode D also becomes forward biased (conductive) whenever the anode voltage at the terminal A of lamp L, falls a few tenths of a volt below the voltage across the capacitor C Capacitor C, will then discharge through resistor R, and either the collector-to-emitter circuit of transistor Q, (when conductive) or through any low resistance device or element connected to terminal 3 and certain of the other circuit components. This similarly requires the programmed delay period for the capacitor C to charge whenever a permissible charge condition for capacitor C is subsequently allowed.

Whenever a relatively low resistance path to ground is applied to the terminal 3, this causes the voltage at the anode terminal A of lamp L, to drop below the maintaining voltage level and therefore deionizes lamp L,. Deionization of lamp L, removes the control voltage V normally available at the terminal 4, as well as the forward bias normally applied to the base of the transistor 0 The removal of forward bias from transistor Q2 causes it to become non-conducting and to place the resistor R in circuit with the resistor R,, thus increasing the voltage V, at the junction 12. This causes the transistor 0, to become forward biased (conducting) fora period of time in accordance with the time constant of the RC circuit defined by capacitor C and the parallel resistance value of resistor R and the input resistance of transistor 0,. This provides a feedback arrangement that enhances the discharging of capacitor C, through the momentary low resistance path provided by the collector-to-emitter circuit of transistor It will thus be seen that in normal operation, when terminal 3 is grounded, either by actuating the manual switch device L, or by turning on either of the transistors Q; or 0,, the maintaining voltage is removed from the anode terminal A of lamp L, causing the lamp to become deionized and thus remove the control voltage V from the output terminal 4. This discharges the capacitor C in the manner above-described. When the low resistance path-to-ground is removed subsequently from the terminal 3, the maintaining voltage will be reapplied to the anode terminal A of lamp L,, but the lamp will not ionize until the capacitor C, has charged to the required triggering voltage necessary at terminal G. Thus, a time delay is provided to restore the control voltage V,. at the terminal 4 after the reset terminal 3 becomes ungrounded. Similarly, this time delay is also required when power is reapplied to the terminals 1 and 2 after removal thereof. Thus, when the power supply at the terminals 1 and 2 is cut off for a period longer than that required for capacitor C, to discharge sufficiently to drop the voltage at the anode terminal A below the maintaining level, the lamp L, will become extinguished and remove the control voltage V,- from the output terminal 4. This control voltage will remain at terminal 4 if the power supply interruption is less than this required time.

After removal of the control voltage V,, as above described, when the supply voltage is again applied to the terminals 1 and 2, the control voltage V will not return until capacitor C, has charged sufficiently to provide the required triggering voltage at the gate electrode G. The lamp L, becomes illuminated (ionized) upon such triggering, and simultaneously the control voltage V, returns to the output terminal 4. The illumination of the lamp L, thus provides an indication of the presence of the control voltage V, at terminal 4.

Many useful applications of the above-described timing circuit will become apparent to those skilled in the art. The flexibility provided by the DC output control voltage, remotely controlled on-delay programming, remotely controlled muting, and resetting, the high degree of immunity to noise, the programmable off-delay (when the source power is removed), the quick of "switching (when muted or reset), the visual indication of the timed-out" condition, and the accurate timing with wide variations of input line source voltage and quick resetting of the timing elements allows for a broad range of timing control applications. One example would be to limit the time for restoration of power to an electrical or electronic device or system following the remote sensing and subsequent muting of this timing circuit. Another example would be to control a semi-conductor type circuit to invert the on delay functions, that is, to cause a circuit system or device to become energized during the timing-out period and deenergized during the timed-out period.

While a specific embodiment of an improved timing circuit has been disclosed in the foregoing description, it will be understood that various modifications within the spirit of the invention may occur to those skilled in the art. Therefore, it is intended that no limitations be placed on the invention except as defined by the scope of the appended claims.

What is claimed is:

l. A timing circuit comprising a gaseous glow discharge lamp having an anode, a cathode and a trigger electrode, an energizing circuit including a source of direct current connected to said anode and cathode and including a terminating impedance across which a device-controlling voltage is developed when the lamp is ionized, means to provide a maintaining voltage across said anode and cathode sufficient to maintain ionization, a triggering circuit branch connected to said energizing circuit and including a resistor and capacitor in series, means connecting the junction of said resistor and capacitor to the triggering electrode, said triggering circuit branch developing a triggering voltage at said triggering electrode after a predetermined period of charging of said capacitor sufficient to cause ionization of the lamp, a diode connected between said junction and said anode, and a second capacitor connected between said anode and a portion of the energizing circuit to sustain said maintaining voltage for a second predetermined period of time when the source of current is removed.

2. The timing circuit of claim 1, and a controlled rapid-discharge circuit branch connected across said second capacitor to at times rapidly remove said devicecontrolling voltage.

3. The timing circuit of claim 2, and wherein said controlled circuit branch includes a manually operated switch.

4. The timing circuit of claim 2, and wherein said controlled circuit branch includes an electronic switch device.

5. The timing circuit of claim 2, and wherein said energizing circuit is provided with a pair of input terminals and a series-connected rectifier at one terminal, and a filter capacitor connected between the output of the rectifier and the other terminal.

6. The timing circuit of claim 2, and respective zenercontrolled voltage stabilizing means connected to said anode and to said triggering circuit branch.

7. The timing circuit of claim 2, and wherein said energizing circuit includes a voltage-divider branch, a transistor connected across said second capacitor, switch means normally shunting a portion of the voltage-divider branch, means to open said switch means responsive to deionization of the lamp, and means to render said transistor conductive responsive to opening said switch means, whereby to enhance the discharging of the first-named capacitor through said diode when the lamp becomes deionized.

8. The timing circuit of claim 7, and wherein said means to render said transistor conductive comprises circuit means connecting the base of said transistor to said voltage-divider branch.

9. The timing circuit of claim 8, and wherein said circuit means connecting the base of said transistor to said voltage-divider branch comprises a series capacitor and a discharge resistor connected across the base and emitter of the transistor.

10. The timing circuit of claim 8, and wherein said switch means comprises a second transistor connected across said portion of the voltage-divider branch, and circuit means connecting the device-controlling voltage terminal of the terminating impedance to the base of said second transistor so as to remove forward bias from said last-named base when the device-controlling voltage is removed. 

1. A timing circuit comprising a gaseous glow discharge lamp having an anode, a cathode and a trigger electrode, an energizing circuit including a source of direct current connected to said anode and cathode and including a terminating impedance across which a device-controlling voltage is developed when the lamp is ionized, means to provide a maintaining voltage across said anode and cathode sufficient to maintain ionization, a triggering circuit branch connected to said energizing circuit and including a resistor and capacitor in series, means connecting the junction of said resistor and capacitor to the triggering electrode, said triggering circuit branch developing a triggering voltage at said triggering electrode after a predetermined period of charging of said capacitor sufficient to cause ionization of the lamp, a diode connected between said junction and said anode, and a second capacitor connected between said anode and a portion of the energizing circuit to sustain said maintaining voltage for a second predetermined period of time when the source of current is removed.
 2. The timing circuit of claim 1, and a controlled rapid-discharge circuit branch connected across said second capacitor to at times rapidly remove said device-controlling voltage.
 3. The timing circuit of claim 2, and wherein said controlled circuit branch includes a manually operated switch.
 4. The timing circuit of claim 2, and wherein said controlled circuit branch includes an electronic switch device.
 5. The timing circuit of claim 2, and wherein said energizing circuit is provided with a pair of input terminals and a series-connected rectifier at one terminal, and a filter capacitor connected between the output of the rectifier and the other terminal.
 6. The timing circuit of claim 2, and respective zener-controlled voltage stabilizing means connected to said anode and to said triggering circuit branch.
 7. The timing circuit of claim 2, and wherein said energizing circuit includes a voltage-divider branch, a transistor connected across said second capacitor, switch means normally shunting a portion of the voltage-divider branch, means to open said switch means responsive to deionization of the lamp, and means to render said transistor conductive responsive to opening said switch means, whereby to enhance the discharging of the first-named capacitor through said diode when the lamp becomes deionized.
 8. The timing circuit of claim 7, and wherein said means to render said transistor conductive comprises circuit means connecting the base of said transistor to said voltage-divider branch.
 9. The timing circuit of claim 8, and wherein said circuit means connecting the base of said transistor to said voltage-divider branch comprises a series capacitor and a discharge resistor connected across the base and emitter of the transistor.
 10. The timing circuit of claim 8, and wherein said switch means comprises a second transistor connected across said portion of the voltage-divider branch, and circuit means connecting the device-controlling voltage terminal of the terminating impedance to the base of Said second transistor so as to remove forward bias from said last-named base when the device-controlling voltage is removed. 